#!/usr/bin/python
# -*- coding: utf-8 -*-
'''
输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。
'''
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def reConstructBinaryTree(self, pre, tin):
        # 根节点为先序遍历第一个数
        if pre and tin:
            root = TreeNode(pre[0])
            #在中序遍历中找到根节点位置
            root_pos_in_tin = tin.index(root.val)
            #确定左子树和右子树长度
            left_length = root_pos_in_tin
            right_length = len(tin) - 1 - root_pos_in_tin
            #递归
            if left_length > 0:
                root.left = Solution().reConstructBinaryTree(pre[1:root_pos_in_tin + 1], tin[0:root_pos_in_tin])
            if right_length > 0:
                root.right = Solution().reConstructBinaryTree(pre[root_pos_in_tin + 1:], tin[root_pos_in_tin + 1:])

        return root